The goal of the proposed research is to understand the role of T cell mediated immunity (CMI) in the lungs for the purpose of developing more rational approaches to vaccination against pulmonary pathogens that are controlled by CMI and designing adjuncts, such as recombinant cytokine administration, to traditional antibiotic treatment of opportunistic infections. A pulmonary infection model for CMI was developed using a low virulence strain of the fungus Cryptococcus neoformans (Cne). The current proposal is based on observations using this model that both CD4 and CD8 T cells are required for protective pulmonary immunity, the protective response is genetically restricted, i.e., occurs in immunocompetent Balb/c mice, but not in immunocompetent C57BL/6 mice, and is associated with T cell dependent lung recruitment and activation of effector macrophages (Mphi). First, early aspects of the pulmonary immune response to Cne will be compared in resistant Balb/c and sensitive C57BL/6 mice to determine what the critical features of the protective T cell immune response in Balb/c mice might be. The approach will be to characterize cytokine secretion profiles of T cells from draining lymph nodes and lung to determine whether T cells from each mouse strain predominantly mediate delayed type hypersensitivity-like responses (TH1 T cells) or antibody and IgE hypersensitivity-like responses (TH2 T cells). Cne specific T cells will be cloned, their cytokine secretion patterns characterized, and used in adoptive transfer experiments to examine their roles in pulmonary Cne clearance in vivo. Second, the role of adhesion molecules involved in the recruitment of both lymphocytes and effector Mphi into Cne infected lungs will be examined. the expression of selected adhesion molecules will be documented and recruitment of mononuclear cells will be manipulated by in vivo administration of monoclonal antibodies to relevant adhesion molecules. Third, whether the potent cytostatic mechanism involving NO production by activated lung Mphi is essential for optimal clearance of Cne from the lungs will be determined using an in vivo inhibitor of NO synthesis. Last, the role of lung DC in regulating immune response to Cne will be assessed by determining whether lung DC show a preferential ability to induce TH1 vs TH2 cells and whether Cne antigen bearing pulmonary DC injected into the tracheas of mice will initiate pulmonary CMI.